1PCS TECO RHN-10K Thermal Overload Relay (8.5–12.5A) — Motor Protection for TECO CN-Series Contactors

TECO · RHN Series · Thermal Overload Relay · 8.5–12.5 A · In stock

The TECO RHN-10K is a thermal bimetal-strip overload relay manufactured by TECO Electric & Machinery (Taiwan). It is designed to protect 3-phase induction motors drawing between 8.5 and 12.5 A by sensing the heat generated in three matched bimetal elements — a classic, time-proven method of motor current protection. The unit clicks directly under a TECO CN-series contactor to form a complete direct-on-line starter, which is why it shows up in so many factory automation panels worldwide. It carries differential phase-loss detection, ambient temperature compensation, and both auto and manual reset modes, plus a front-panel test button that lets the commissioning engineer simulate a trip without driving the motor.

Need a quote, a cross-reference, or a full BOM including the matching contactor, push buttons and wiring duct? Send the list to Moritta@KOEED.COM and the team will reply with stock and price within 24 hours on business days.

1. Key Technical Specifications & Overview

Internally, three matched bimetal strips are heated by the motor phase currents. When sustained overcurrent heats the strips past their trip threshold, the differential lever flips the auxiliary contacts, dropping the contactor coil. Phase-loss protection is achieved by a differential lever: if one phase is lost, the unbalanced heating causes a faster trip, which prevents the single-phasing burn-out that kills motor windings within minutes.

2. Application Scenarios — Where the RHN-10K Fits

The 8.5–12.5 A window lines up with the most common 3-phase induction motors found on the plant floor. Typical deployments include:

• Pumps — centrifugal, booster and submersible pumps in water and wastewater treatment plants.
• Fans and blowers — AHU return fans, exhaust blowers, induced-draft fans.
• Conveyors — packaging lines, material handling and palletiser feed conveyors.
• Machine tools — coolant pumps, hydraulic power units, spindle oil coolers.
• HVAC — chilled-water circulation pumps and cooling-tower fans.
• Compressors — small reciprocating and screw air compressors up to 7.5 kW.

The RHN-10K is commonly wired into motor starter buckets that are themselves controlled by a PLC or HMI from one of the nine brands KOEED distributes — Allen-Bradley, Siemens, Mitsubishi, Omron, Fanuc, Schneider, Yaskawa, Panasonic, and KEYENCE. The TECO relay's NC trip contact feeds a digital input on the controller, the NO contact lights an HMI alarm, and the contactor's coil is driven by a 24 V DC or 110/220 V AC output — a textbook direct-on-line starter arrangement.

When replacing an aging Telemecanique, Fuji or LS thermal relay, the RHN-10K is a frequent drop-in candidate because the 8.5–12.5 A range covers the most popular mid-frame motor sizes on the EU 400 V grid. If you are not sure which frame to specify, the KOEED AI Diagnostic Tool can read a nameplate photo and recommend a matching part number.

3. Integration & Wiring Notes

The RHN-10K is designed for direct mounting beneath a TECO CN-11, CN-12 or CN-13 contactor. Three pass-through power terminals (L1 / L2 / L3) feed the relay's bimetal elements and exit straight to the contactor output, so the main three-phase loop does not need extra jumper wires. The wiring pattern is:

• Power circuit: supply → relay input (L1/L2/L3) → relay output → contactor input → motor terminals (U/V/W).
• Auxiliary contacts (front face): 95–96 NC and 97–98 NO, both rated for control-circuit duty.
• Control circuit: the NC contact is wired in series with the contactor coil so that a thermal trip drops the coil and removes power from the motor.
• Alarm circuit: the NO contact can be wired to a PLC digital input, an indicator lamp, or a remote alarm horn to signal "overload tripped".
• Reset wiring: no external wiring is needed; the AUTO / MANUAL selector is on the relay's front face.

The differential phase-loss protection requires no special wiring — it operates on the imbalance of the three bimetal currents inside the relay itself. This is one of the key reasons engineers prefer thermal-class relays over simple bi-metallic fuses for three-phase motor protection. For control cabinets that have to be wired in tight spaces, a typical BOM also includes terminal blocks, ferrules and DIN-rail wiring ducts that the KOEED team can quote alongside the relay if you send the full instrument list to Moritta@KOEED.COM.

If you intend to mount the relay on a 35 mm DIN-rail (rather than directly under a TECO contactor), fit the optional DIN-rail adapter plate. When replacing an older LRE or 3UA series relay from a different brand, the cross-reference team at KOEED can map terminal numbers 95 / 96 / 97 / 98 to the equivalent terminals on your existing contactor.

4. Installation & Commissioning Tips

A correct commissioning sequence protects the motor and reduces nuisance trips. KOEED recommends the following steps when installing an RHN-10K:

1. Set the current dial to the motor's nameplate full-load current (FLC). For a 7.5 kW / 400 V motor drawing roughly 14 A, the RHN-10K is actually too small — step up to the RHN-20K (15–21 A) or RHN-30K frame instead.
2. Select AUTO or MANUAL reset before energising. AUTO is normal for unattended pumps and fans; MANUAL is mandatory on conveyors and machine tools where a sudden restart could injure an operator.
3. Verify the TEST button with the contactor coil un-powered: pressing TEST should flip the auxiliary contacts and you should hear an audible click. If the trip flag does not change, the relay is faulty and must be replaced.
4. Run a no-load bump test for 2–3 seconds and confirm that the motor spins in the correct direction. A 3-phase phase-sequence error (motor runs backwards) is not the relay's job to catch — install a phase-sequence relay upstream if rotation matters.
5. Check the ambient temperature compensation. The RHN-10K is compensated for ambient swings between roughly −5 °C and +40 °C. Outside this range, expect longer or shorter trip times; consider the AI Diagnostic Tool for derating guidance.
6. Document the setting on the panel legend so that future maintenance engineers can re-verify it after a trip event.

If the relay trips repeatedly on start-up, the most common culprits are (a) current dial set too low, (b) locked-rotor condition on a heavy-load machine, or (c) phase loss upstream. The PLC Error Code Database on the KOEED website is a useful reference when a Siemens or Mitsubishi HMI throws an overload alarm and the operator is unsure whether the fault is in the drive, the contactor, or the relay.

5. Procurement, Warranty & Lead Time

KOEED operates on a quote-driven, B2B model rather than fixed online pricing. For a single piece or a 500-piece panel build, the workflow is the same: send a part number list and the team will reply with stock position, lead time, and tiered pricing within 24 hours on business days. KOEED does not list fixed prices for this relay because pricing varies with quantity, destination, and Incoterms — but the Create a Quote form on the website is the fastest way to get a firm number.

Authenticity. TECO RHN-10K relays sourced from KOEED are genuine factory-original parts pulled from authorised channels. Each shipment can be accompanied by a manufacturer datasheet on request, and the part is covered by the standard KOEED warranty against manufacturing defect.

Lead time. In-stock items typically ship within 1–3 business days from the Shenzhen / Hong Kong dual-base warehouse. Worldwide shipping is available via DHL, FedEx, UPS, and standard air freight; transit time depends on destination but most regions receive orders within 3–7 days door-to-door.

Full-BOM support. The relay is rarely ordered alone — a typical motor starter bucket also includes a contactor, a motor circuit breaker, push buttons, selector switches, terminal blocks, and often a PLC or HMI. Send the entire instrument list to Moritta@KOEED.COM and KOEED will quote the lot as one BOM, mixing brands such as TECO contactors, TECO relays, and a controller from any of the nine brands KOEED distributes.

For engineering questions, panel-design help, or a cross-reference against an older Telemecanique, Fuji, LS, Eaton or Moeller relay, the Contact Us page lists every channel — email, WhatsApp, and the online form. The FAQ page also has answers to the most common "which frame to choose" and "how to wire a 3-phase starter" questions.

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